It is already known to use an epoxy-based conductive adhesive to electrically connect the terminals of the components to conductive tracks, e.g. on a printed circuit board. For this purpose, the fluid adhesive is applied by screen printing, the components are stuck into the tacky adhesive, and the adhesive is subsequently cured, for example at 150 degrees Celsius. This has the disadvantage that only a limited time, dependent upon the hardening time of the adhesive, may be permitted to elapse between the application of the adhesive and the placement of the components. Furthermore, once the adhesive has hardened on them, components can only be removed by mechanically prying them out, possibly assisted by temperature, e.g. heating the adhesive. This involves a risk that the substrate and/or nearby components will be damaged.
In the case of hybrid technology circuits, in which one fraction of the electronic components are adhered and the rest are soldered in place, this method can no longer be used, since one begins with solder paste printed onto the substrate, and subsequent screen printing of conductive adhesive smears the solder paste.
It is also known, from an article in the journal Microelectronic Manufacturing and Testing, June 1988, entitled "Thermal Stress Reduction Via Thermoplastic Die-Attach Adhesive" to use a meltable adhesive for assembly of integrated circuits (IC's). However, it is not applied as a fluid, but rather in solid form as flakes and only then melted onto the substrate. This has the disadvantage that, for each IC, the adhesive flake must be individually positioned.
The aforementioned I.S.H.M. article, "A Reworkable High Reliability Thermoplastic Die Attach Adhesive", teaches a method according to which the screen-printed adhesive can be dissolved in a solvent, the solvent subsequently being evaporated.